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Amor Z, Le Ster C, Gr C, Daval-Frérot G, Boulant N, Mauconduit F, Thirion B, Ciuciu P, Vignaud A. Impact of B 0 $$ {\mathrm{B}}_0 $$ field imperfections correction on BOLD sensitivity in 3D-SPARKLING fMRI data. Magn Reson Med 2024; 91:1434-1448. [PMID: 38156952 DOI: 10.1002/mrm.29943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/07/2023] [Accepted: 11/09/2023] [Indexed: 01/03/2024]
Abstract
PURPOSE Static and dynamicB 0 $$ {\mathrm{B}}_0 $$ field imperfections are detrimental to functional MRI (fMRI) applications, especially at ultra-high magnetic fields (UHF). In this work, a field camera is used to assess the benefits of retrospectively correctingB 0 $$ {\mathrm{B}}_0 $$ field perturbations on Blood Oxygen Level Dependent (BOLD) sensitivity in non-Cartesian three-dimensional (3D)-SPARKLING fMRI acquisitions. METHODS fMRI data were acquired at 1 mm3 $$ {}^3 $$ and for a 2.4s-TR while concurrently monitoring in real-time field perturbations using a Skope Clip-on field camera in a novel experimental setting involving a shorter TR than the required minimal TR of the field probes. Measurements of the dynamic field deviations were used along with a staticΔ B 0 $$ \Delta {\mathrm{B}}_0 $$ map to retrospectively correct static and dynamic field imperfections, respectively. In order to evaluate the impact of such a correction on fMRI volumes, a comparative study was conducted on healthy volunteers. RESULTS Correction ofB 0 $$ {\mathrm{B}}_0 $$ deviations improved image quality and yielded between 20% and 30% increase in median temporal signal-to-noise ratio (tSNR).Using fMRI data collected during a retinotopic mapping experiment, we demonstrated a significant increase in sensitivity to the BOLD contrast and improved accuracy of the BOLD phase maps: 44% (resp., 159%) more activated voxels were retrieved when using a significance control level based on a p-value of 0.001 without correcting for multiple comparisons (resp., 0.05 with a false discovery rate correction). CONCLUSION 3D-SPARKLING fMRI hugely benefits from static and dynamicB 0 $$ {\mathrm{B}}_0 $$ imperfections correction. However, the proposed experimental protocol is flexible enough to be deployed on a large spectrum of encoding schemes, including arbitrary non-Cartesian readouts.
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Affiliation(s)
- Zaineb Amor
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Caroline Le Ster
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Chaithya Gr
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
| | - Guillaume Daval-Frérot
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
- Siemens Healthineers, Courbevoie, France
| | - Nicolas Boulant
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Franck Mauconduit
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Bertrand Thirion
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
| | - Philippe Ciuciu
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
- Inria, MIND, Palaiseau, France
| | - Alexandre Vignaud
- CEA, NeuroSpin, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
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Dubovan PI, Gilbert KM, Baron CA. A correction algorithm for improved magnetic field monitoring with distal field probes. Magn Reson Med 2023; 90:2242-2260. [PMID: 37598420 DOI: 10.1002/mrm.29781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 05/15/2023] [Accepted: 06/12/2023] [Indexed: 08/22/2023]
Abstract
PURPOSE A significant source of artifacts in MRI are field fluctuations. Field monitoring is a new technology that allows measurement of field dynamics during a scan via "field probes," which can be used to improve image reconstruction. Ideally, probes are located within the volume where gradients produce nominally linear field patterns. However, in some situations probes must be located far from isocenter where rapid field variation can arise, leading to erroneous field-monitoring characterizations and images. This work aimed to develop an algorithm that improves the robustness of field dynamics in these situations. METHODS The algorithm is split into three components. Component 1 calculates field dynamics one spatial order at a time, whereas the second implements a weighted least squares solution based on probe distance. Component 3 then calculates phase residuals and removes the residual phase for distant probes before recalculation. Two volunteers and a phantom were scanned on a 7T MRI using diffusion-weighted sequences, and field monitoring was performed. Image reconstructions were informed with field dynamics calculated conventionally, and with the correction algorithm, after which in vivo images were compared qualitatively and phantom image error was quantitatively assessed. RESULTS The algorithm was able to correct corrupted field dynamics, resulting in image-quality improvements. Significant artifact reduction was observed when correcting higher-order fits. Stepwise fitting provided the most correction benefit, which was marginally improved when adding the other correction strategies. CONCLUSION The proposed algorithm can mitigate effects of phase errors in field monitoring, providing improved characterization of field dynamics.
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Affiliation(s)
- Paul I Dubovan
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Center for Functional and Metabolic Mapping, Western University, London, Ontario, Canada
| | - Kyle M Gilbert
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Center for Functional and Metabolic Mapping, Western University, London, Ontario, Canada
| | - Corey A Baron
- Department of Medical Biophysics, Western University, London, Ontario, Canada
- Center for Functional and Metabolic Mapping, Western University, London, Ontario, Canada
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Seginer A, Schmidt R. Messing up to clean up: Semi-randomized frequency selective space-filling curves to suppress physiological signal fluctuations in MRI. Magn Reson Med 2023; 90:2275-2289. [PMID: 37448104 DOI: 10.1002/mrm.29790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 06/19/2023] [Accepted: 06/20/2023] [Indexed: 07/15/2023]
Abstract
PURPOSE Rapid 3D steady-state sequences are widely used but are also known to be sensitive to semi-periodic physiological signal fluctuations due to, for example, cardiac pulsation, breathing, and eye/eyelids movement. This semi-periodicity results in repeating artifacts in the image whose intensity depends on the scan parameters. The purpose of this study is to design a reordering of the 2D phase encodes (within the 3D acquisition) that reduces these artifacts. METHODS A randomized order of the phase encodes can suppress repeating artifact but may also introduce its own apparent noise, for example, in cases of slow subject movement or gradual changes in eddy currents. In a new design a semi-randomized space-filling curve is generated by scrambling the local order of the phase encodes to achieve a controlled frequency selective effect, that is, eliminating artifacts above a chosen (fluctuation) frequency threshold while leaving lower frequencies untouched, thus overcoming the limitations of a randomized order. The method was characterized in simulations and substantiated by human brain imaging at 7 T using two steady-state gradient echo variants that suffer from pulsation, either near blood vessels or near the ventricles. RESULTS The simulations with a point source show that the maximum artifact intensity can be reduced by factors of 10-50 depending on the scan parameters. In human scanning, the new approach drastically reduced physiologically induced artifacts and was superior in this regard to both full randomization and a generalized Hilbert curve, another semi-randomized approach. CONCLUSION The phase-encodes reordering presented here effectively removes artifacts arising from local fluctuations.
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Affiliation(s)
- Amir Seginer
- Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
- The Azrieli National Institute for Human Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel
| | - Rita Schmidt
- The Azrieli National Institute for Human Brain Imaging and Research, Weizmann Institute of Science, Rehovot, Israel
- Department of Brain Sciences, Weizmann Institute of Science, Rehovot, Israel
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Çavuşoğlu M. Arterial spin labeling MRI using spiral acquisitions and concurrent field monitoring. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 356:107572. [PMID: 37847985 DOI: 10.1016/j.jmr.2023.107572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 09/25/2023] [Accepted: 10/09/2023] [Indexed: 10/19/2023]
Abstract
Perfusion MRI based on arterial spin labeling (ASL) has intrinsically very low signal-to-noise ratio (SNR). Signal acquisition at shorter echo times (TE) is necessary to boost the SNR of the ASL images. Spiral trajectories provide substantially shorter TE yielding increased SNR and are among the fastest k-space sampling schemes to encode a given field of view and resolution. Moreover, they provide approximately isotropic point-spread functions and inherent refocusing of motion- and flow-induced phase errors. However, the efficiency of the spiral acquisitions in ASL-MRI has been limited because these advantages are counterbalanced by practical technical challenges. This is because spiral acquisitions are highly sensitive to encoding deficiencies such as static off-resonance in the main magnetic field manifested as blurring artifacts in the image. Moreover, deviation of the gradient fields from the nominal waveforms due to the imperfection of the employed hardware critically limits the practical utilization of spiral trajectories. In this work, I provide single- and multiple-shot spiral ASL images that are robust against typical spiral encoding drawbacks enabled by deploying a comprehensive signal model involving static off-resonance and coil sensitivity maps and actual B0 and gradient field dynamics up to third order in space. The spiral ASL signal acquisition was concurrently monitored using a 3rd order dynamic field camera based on NMR field probes. The reconstructed ASL images at 3 mm and 2 mm in-plane resolution associating with the monitored field dynamics and the static off-resonances exhibited strongly reduced blurring- and aliasing artifacts and distortion. Concurrent field monitoring also enables to account for quasi-static B0 drifts by encompassing the parametric input data with consistent encoding geometry and physiological field fluctuations. In conclusion, concurrent field monitoring in spiral ASL acquisition largely overcomes traditional vulnerability of spiral trajectories in practice providing high quality ASL images with increased SNR, speed and motion robustness.
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Affiliation(s)
- Mustafa Çavuşoğlu
- Institute for Biomedical Engineering, University and ETH Zürich, Zürich, Switzerland; Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, University of Zurich, Switzerland.
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Fritz FJ, Mordhorst L, Ashtarayeh M, Periquito J, Pohlmann A, Morawski M, Jaeger C, Niendorf T, Pine KJ, Callaghan MF, Weiskopf N, Mohammadi S. Fiber-orientation independent component of R 2* obtained from single-orientation MRI measurements in simulations and a post-mortem human optic chiasm. Front Neurosci 2023; 17:1133086. [PMID: 37694109 PMCID: PMC10491021 DOI: 10.3389/fnins.2023.1133086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 08/04/2023] [Indexed: 09/12/2023] Open
Abstract
The effective transverse relaxation rate (R2*) is sensitive to the microstructure of the human brain like the g-ratio which characterises the relative myelination of axons. However, the fibre-orientation dependence of R2* degrades its reproducibility and any microstructural derivative measure. To estimate its orientation-independent part (R2,iso*) from single multi-echo gradient-recalled-echo (meGRE) measurements at arbitrary orientations, a second-order polynomial in time model (hereafter M2) can be used. Its linear time-dependent parameter, β1, can be biophysically related to R2,iso* when neglecting the myelin water (MW) signal in the hollow cylinder fibre model (HCFM). Here, we examined the performance of M2 using experimental and simulated data with variable g-ratio and fibre dispersion. We found that the fitted β1 can estimate R2,iso* using meGRE with long maximum-echo time (TEmax ≈ 54 ms), but not accurately captures its microscopic dependence on the g-ratio (error 84%). We proposed a new heuristic expression for β1 that reduced the error to 12% for ex vivo compartmental R2 values. Using the new expression, we could estimate an MW fraction of 0.14 for fibres with negligible dispersion in a fixed human optic chiasm for the ex vivo compartmental R2 values but not for the in vivo values. M2 and the HCFM-based simulations failed to explain the measured R2*-orientation-dependence around the magic angle for a typical in vivo meGRE protocol (with TEmax ≈ 18 ms). In conclusion, further validation and the development of movement-robust in vivo meGRE protocols with TEmax ≈ 54 ms are required before M2 can be used to estimate R2,iso* in subjects.
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Affiliation(s)
- Francisco J. Fritz
- Department of Systems Neurosciences, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Laurin Mordhorst
- Department of Systems Neurosciences, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Mohammad Ashtarayeh
- Department of Systems Neurosciences, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Joao Periquito
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Andreas Pohlmann
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Markus Morawski
- Paul Flechsig Institute – Center for Neuropathology and Brain Research, University of Leipzig, Leipzig, Germany
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Carsten Jaeger
- Paul Flechsig Institute – Center for Neuropathology and Brain Research, University of Leipzig, Leipzig, Germany
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Thoralf Niendorf
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrueck-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Kerrin J. Pine
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Martina F. Callaghan
- Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, United Kingdom
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany
| | - Siawoosh Mohammadi
- Department of Systems Neurosciences, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- Max Planck Research Group MR Physics, Max Planck Institute for Human Development, Berlin, Germany
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Chan KS, Chamberland M, Marques JP. On the performance of multi-compartment relaxometry for myelin water imaging (MCR-MWI) - test-retest repeatability and inter-protocol reproducibility. Neuroimage 2023; 266:119824. [PMID: 36539169 DOI: 10.1016/j.neuroimage.2022.119824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 12/14/2022] [Accepted: 12/16/2022] [Indexed: 12/23/2022] Open
Abstract
In this study, we optimized the variable flip angle (VFA) acquisition scheme using numerical simulations to shorten the acquisition time of multicompartment relaxometry for myelin water imaging (MCR-MWI) to a clinically practical range in the absence of advanced image reconstruction methods. As the primary objective of this study, the test-retest repeatability of myelin water fraction (MWF) measurements of MCR-MWI is evaluated on three gradient echo (GRE) sequence settings using the optimized VFA schemes with different echo times and repetition times, emulating various scanner setups. The cross-protocol reproducibility of MCR-MWI and MCR with diffusion-informed myelin water imaging (MCR-DIMWI) is also examined. As a secondary objective, we explore the bundle-specific profiles of various microstructural parameters from MCR-(DI)MWI and their cross-correlations to determine if these parameters possess supplementary microstructure information beyond myelin concentration. Numerical simulations indicate that MCR-MWI can be performed with a minimum of three flip angles covering a wide range of T1 weightings without adding significant bias. This is supported by the results of an in vivo experiment, allowing whole-brain 1.5 mm isotropic MWF maps to be acquired in 9 min, reducing the total scan time to 40% of the original implementation without significant quality degradation. Good test-retest repeatability is observed for MCR-MWI for all three GRE protocols. While good correlations can also be found in MWF across protocols, systematic differences are observed. Bundle-specific MWF analysis reveals that certain white matter bundles are similar in all participants. We also found that microstructure relaxation parameters have low linear correlations with MWF. MCR-MWI is a reproducible measure of myelin. However, attention should be paid to the protocol related MWF differences when comparing different studies, as the MWF bias up to 0.5% can be observed across the protocols examined in this work.
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Affiliation(s)
- Kwok-Shing Chan
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN, Nijmegen, the Netherlands
| | - Maxime Chamberland
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN, Nijmegen, the Netherlands
| | - José P Marques
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, 6525 EN, Nijmegen, the Netherlands.
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Vaculčiaková L, Podranski K, Edwards LJ, Ocal D, Veale T, Fox NC, Haak R, Ehses P, Callaghan MF, Pine KJ, Weiskopf N. Combining navigator and optical prospective motion correction for high-quality 500 μm resolution quantitative multi-parameter mapping at 7T. Magn Reson Med 2022; 88:787-801. [PMID: 35405027 DOI: 10.1002/mrm.29253] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Revised: 03/10/2022] [Accepted: 03/10/2022] [Indexed: 12/15/2022]
Abstract
PURPOSE High-resolution quantitative multi-parameter mapping shows promise for non-invasively characterizing human brain microstructure but is limited by physiological artifacts. We implemented corrections for rigid head movement and respiration-related B0-fluctuations and evaluated them in healthy volunteers and dementia patients. METHODS Camera-based optical prospective motion correction (PMC) and FID navigator correction were implemented in a gradient and RF-spoiled multi-echo 3D gradient echo sequence for mapping proton density (PD), longitudinal relaxation rate (R1) and effective transverse relaxation rate (R2*). We studied their effectiveness separately and in concert in young volunteers and then evaluated the navigator correction (NAVcor) with PMC in a group of elderly volunteers and dementia patients. We used spatial homogeneity within white matter (WM) and gray matter (GM) and scan-rescan measures as quality metrics. RESULTS NAVcor and PMC reduced artifacts and improved the homogeneity and reproducibility of parameter maps. In elderly participants, NAVcor improved scan-rescan reproducibility of parameter maps (coefficient of variation decreased by 14.7% and 11.9% within WM and GM respectively). Spurious inhomogeneities within WM were reduced more in the elderly than in the young cohort (by 9% vs. 2%). PMC increased regional GM/WM contrast and was especially important in the elderly cohort, which moved twice as much as the young cohort. We did not find a significant interaction between the two corrections. CONCLUSION Navigator correction and PMC significantly improved the quality of PD, R1, and R2* maps, particularly in less compliant elderly volunteers and dementia patients.
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Affiliation(s)
- Lenka Vaculčiaková
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Kornelius Podranski
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Luke J Edwards
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Dilek Ocal
- The Dementia Research Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, London, UK
| | - Thomas Veale
- The Dementia Research Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, London, UK.,UK Dementia Research Institute at UCL, UCL, London, UK
| | - Nick C Fox
- The Dementia Research Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, London, UK.,UK Dementia Research Institute at UCL, UCL, London, UK
| | - Rainer Haak
- Department of Cariology, Endodontology and Periodontology, University of Leipzig, Leipzig, Germany
| | - Philipp Ehses
- Department of MR Physics, German Center for Neurodegenerative Diseases, Bonn, Germany
| | - Martina F Callaghan
- The Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Kerrin J Pine
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,The Wellcome Centre for Human Neuroimaging, UCL Queen Square Institute of Neurology, University College London, London, UK.,Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany
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8
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Gilbert KM, Dubovan PI, Gati JS, Menon RS, Baron CA. Integration of an RF coil and commercial field camera for ultrahigh-field MRI. Magn Reson Med 2021; 87:2551-2565. [PMID: 34932225 DOI: 10.1002/mrm.29130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/16/2021] [Accepted: 12/03/2021] [Indexed: 11/08/2022]
Abstract
PURPOSE To develop an RF coil with an integrated commercial field camera for ultrahigh field (7T) neuroimaging. The RF coil would operate within a head-only gradient coil and be subject to the corresponding design constraints. The RF coil can thereafter be used for subject-specific correction of k-space trajectories-notably in gradient-sensitive sequences such as single-shot spiral imaging. METHODS The transmit and receive performance was evaluated before and after the integration of field probes, whereas field probes were evaluated when in an optimal configuration external to the coil and after their integration. Diffusion-weighted EPI and single-shot spiral acquisitions were employed to evaluate the efficacy of correcting higher order field perturbations and the consequent effect on image quality. RESULTS Field probes had a negligible effect on RF-coil performance, including the transmit efficiency, transmit uniformity, and mean SNR over the brain. Modest reductions in field-probe signal lifetimes were observed, caused primarily by nonidealities in the gradient and shim fields of the head-only gradient coil at the probe positions. The field-monitoring system could correct up to second-order field perturbations in single-shot spiral imaging. CONCLUSION The integrated RF coil and field camera was capable of concurrent-field monitoring within a 7T head-only scanner and facilitated the subsequent correction of k-space trajectories during spiral imaging.
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Affiliation(s)
- Kyle M Gilbert
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Paul I Dubovan
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Joseph S Gati
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Ravi S Menon
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
| | - Corey A Baron
- Centre for Functional and Metabolic Mapping, The University of Western Ontario, London, Ontario, Canada.,Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada
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Yedavalli V, DiGiacomo P, Tong E, Zeineh M. High-resolution Structural Magnetic Resonance Imaging and Quantitative Susceptibility Mapping. Magn Reson Imaging Clin N Am 2021; 29:13-39. [PMID: 33237013 DOI: 10.1016/j.mric.2020.09.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
High-resolution 7-T imaging and quantitative susceptibility mapping produce greater anatomic detail compared with conventional strengths because of improvements in signal/noise ratio and contrast. The exquisite anatomic details of deep structures, including delineation of microscopic architecture using advanced techniques such as quantitative susceptibility mapping, allows improved detection of abnormal findings thought to be imperceptible on clinical strengths. This article reviews caveats and techniques for translating sequences commonly used on 1.5 or 3 T to high-resolution 7-T imaging. It discusses for several broad disease categories how high-resolution 7-T imaging can advance the understanding of various diseases, improve diagnosis, and guide management.
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Affiliation(s)
- Vivek Yedavalli
- Department of Radiology, Stanford University, 300 Pasteur Drive, Room S047, Stanford, CA 94305-5105, USA; Division of Neuroradiology, Johns Hopkins University, 600 N. Wolfe St. B-112 D, Baltimore, MD 21287, USA
| | - Phillip DiGiacomo
- Department of Bioengineering, Stanford University, Lucas Center for Imaging, Room P271, 1201 Welch Road, Stanford, CA 94305-5488, USA
| | - Elizabeth Tong
- Department of Radiology, 300 Pasteur Drive, Room S031, Stanford, CA 94305-5105, USA
| | - Michael Zeineh
- Department of Radiology, Stanford University, Lucas Center for Imaging, Room P271, 1201 Welch Road, Stanford, CA 94305-5488, USA.
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10
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Marques JP, Meineke J, Milovic C, Bilgic B, Chan K, Hedouin R, van der Zwaag W, Langkammer C, Schweser F. QSM reconstruction challenge 2.0: A realistic in silico head phantom for MRI data simulation and evaluation of susceptibility mapping procedures. Magn Reson Med 2021; 86:526-542. [PMID: 33638241 PMCID: PMC8048665 DOI: 10.1002/mrm.28716] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 01/12/2021] [Accepted: 01/15/2021] [Indexed: 12/14/2022]
Abstract
PURPOSE To create a realistic in silico head phantom for the second QSM reconstruction challenge and for future evaluations of processing algorithms for QSM. METHODS We created a digital whole-head tissue property phantom by segmenting and postprocessing high-resolution (0.64 mm isotropic), multiparametric MRI data acquired at 7 T from a healthy volunteer. We simulated the steady-state magnetization at 7 T using a Bloch simulator and mimicked a Cartesian sampling scheme through Fourier-based processing. Computer code for generating the phantom and performing the MR simulation was designed to facilitate flexible modifications of the phantom in the future, such as the inclusion of pathologies as well as the simulation of a wide range of acquisition protocols. Specifically, the following parameters and effects were implemented: TR and TE, voxel size, background fields, and RF phase biases. Diffusion-weighted imaging phantom data are provided, allowing future investigations of tissue-microstructure effects in phase and QSM algorithms. RESULTS The brain part of the phantom featured realistic morphology with spatial variations in relaxation and susceptibility values similar to the in vivo setting. We demonstrated some of the phantom's properties, including the possibility of generating phase data with nonlinear evolution over TE due to partial-volume effects or complex distributions of frequency shifts within the voxel. CONCLUSION The presented phantom and computer programs are publicly available and may serve as a ground truth in future assessments of the faithfulness of quantitative susceptibility reconstruction algorithms.
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Affiliation(s)
- José P. Marques
- Donders Institute for Brain, Cognition and BehaviorRadboud UniversityNijmegenthe Netherlands
| | | | - Carlos Milovic
- Department of Electrical EngineeringPontificia Universidad Catolica de ChileSantiagoChile
- Biomedical Imaging CenterPontificia Universidad Catolica de ChileSantiagoChile
- Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUnited Kingdom
| | - Berkin Bilgic
- Athinoula A. Martinos Center for Biomedical ImagingCharlestownMassachusettsUSA
- Department of RadiologyHarvard Medical SchoolBostonMassachusettsUSA
- Harvard‐MIT Health Sciences and TechnologyMITCambridgeMassachusettsUSA
| | - Kwok‐Shing Chan
- Donders Institute for Brain, Cognition and BehaviorRadboud UniversityNijmegenthe Netherlands
| | - Renaud Hedouin
- Donders Institute for Brain, Cognition and BehaviorRadboud UniversityNijmegenthe Netherlands
- Centre Inria Rennes ‐ Bretagne AtlantiqueRennesFrance
| | | | | | - Ferdinand Schweser
- Buffalo Neuroimaging Analysis CenterDepartment of NeurologyJacobs School of Medicine and Biomedical SciencesUniversity at BuffaloThe State University of New YorkBuffaloNew YorkUSA
- Center for Biomedical Imaging, Clinical and Translational Science InstituteUniversity at BuffaloThe State University of New YorkBuffaloNew YorkUSA
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Brammerloh M, Morawski M, Friedrich I, Reinert T, Lange C, Pelicon P, Vavpetič P, Jankuhn S, Jäger C, Alkemade A, Balesar R, Pine K, Gavriilidis F, Trampel R, Reimer E, Arendt T, Weiskopf N, Kirilina E. Measuring the iron content of dopaminergic neurons in substantia nigra with MRI relaxometry. Neuroimage 2021; 239:118255. [PMID: 34119638 PMCID: PMC8363938 DOI: 10.1016/j.neuroimage.2021.118255] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/02/2021] [Accepted: 06/07/2021] [Indexed: 12/19/2022] Open
Abstract
Dopaminergic neurons dominate effective transverse relaxation in nigrosome 1. Ion beam microscopy reveals highest iron concentrations in dopaminergic neurons. Developed biophysical model links MRI parameters to cellular iron content. Ferritin- and neuromelanin-bound iron impact MRI parameters differently. Quantitative MRI provides a potential biomarker of iron in dopaminergic neurons.
In Parkinson’s disease, the depletion of iron-rich dopaminergic neurons in nigrosome 1 of the substantia nigra precedes motor symptoms by two decades. Methods capable of monitoring this neuronal depletion, at an early disease stage, are needed for early diagnosis and treatment monitoring. Magnetic resonance imaging (MRI) is particularly suitable for this task due to its sensitivity to tissue microstructure and in particular, to iron. However, the exact mechanisms of MRI contrast in the substantia nigra are not well understood, hindering the development of powerful biomarkers. In the present report, we illuminate the contrast mechanisms in gradient and spin echo MR images in human nigrosome 1 by combining quantitative 3D iron histology and biophysical modeling with quantitative MRI on post mortem human brain tissue. We show that the dominant contribution to the effective transverse relaxation rate (R2*) in nigrosome 1 originates from iron accumulated in the neuromelanin of dopaminergic neurons. This contribution is appropriately described by a static dephasing approximation of the MRI signal. We demonstrate that the R2* contribution from dopaminergic neurons reflects the product of cell density and cellular iron concentration. These results demonstrate that the in vivo monitoring of neuronal density and iron in nigrosome 1 may be feasible with MRI and provide directions for the development of biomarkers for an early detection of dopaminergic neuron depletion in Parkinson’s disease.
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Affiliation(s)
- Malte Brammerloh
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany; International Max Planck Research School on Neuroscience of Communication: Function, Structure, and Plasticity; Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, Leipzig 04103, Germany.
| | - Markus Morawski
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany; Paul Flechsig Institute of Brain Research, University of Leipzig, Liebigstr. 19, Leipzig, 04103, Germany
| | - Isabel Friedrich
- Paul Flechsig Institute of Brain Research, University of Leipzig, Liebigstr. 19, Leipzig, 04103, Germany
| | - Tilo Reinert
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany; Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, Leipzig 04103, Germany
| | - Charlotte Lange
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany; Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, Leipzig 04103, Germany
| | - Primož Pelicon
- Jožef Stefan Institute, Jamova 39, Ljubljana SI-1000, Slovenia
| | - Primož Vavpetič
- Jožef Stefan Institute, Jamova 39, Ljubljana SI-1000, Slovenia
| | - Steffen Jankuhn
- Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, Leipzig 04103, Germany
| | - Carsten Jäger
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany; Paul Flechsig Institute of Brain Research, University of Leipzig, Liebigstr. 19, Leipzig, 04103, Germany
| | - Anneke Alkemade
- Integrative Model-based Cognitive Neuroscience Research Unit, University of Amsterdam, Amsterdam, Nieuwe Achtergracht 129B, 1001 NK Amsterdam, The Netherlands
| | - Rawien Balesar
- Integrative Model-based Cognitive Neuroscience Research Unit, University of Amsterdam, Amsterdam, Nieuwe Achtergracht 129B, 1001 NK Amsterdam, The Netherlands; The Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, Netherlands
| | - Kerrin Pine
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany
| | - Filippos Gavriilidis
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany
| | - Robert Trampel
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany
| | - Enrico Reimer
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany
| | - Thomas Arendt
- Paul Flechsig Institute of Brain Research, University of Leipzig, Liebigstr. 19, Leipzig, 04103, Germany
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany; Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Linnéstr. 5, Leipzig 04103, Germany
| | - Evgeniya Kirilina
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, Leipzig 04103, Germany; Center for Cognitive Neuroscience Berlin, Free University Berlin, Habelschwerdter Allee 45, Berlin, 14195, Germany
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12
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Berglund J, Sprenger T, van Niekerk A, Rydén H, Avventi E, Norbeck O, Skare S. Motion-insensitive susceptibility weighted imaging. Magn Reson Med 2021; 86:1970-1982. [PMID: 34076922 DOI: 10.1002/mrm.28850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 04/07/2021] [Accepted: 04/29/2021] [Indexed: 12/16/2022]
Abstract
PURPOSE To enable SWI that is robust to severe head movement. METHODS Prospective motion correction using a markerless optical tracker was applied to all pulse sequences. Three-dimensional gradient-echo and 3D EPI were used as reference sequences, but were expected to be sensitive to motion-induced B0 changes, as the long TE required for SWI allows phase discrepancies to accumulate between shots. Therefore, 2D interleaved snapshot EPI was investigated for motion-robust SWI and compared with conventional 2D EPI. Repeated signal averages were retrospectively corrected for motion. The sequences were evaluated at 3 T through controlled motion experiments involving two cooperative volunteers and SWI of a tumor patient. RESULTS The performed continuous head motion was in the range of 5-8° rotations. The image quality of the 3D sequences and conventional 2D EPI was poor unless the rotational motion axis was parallel to B0 . Interleaved snapshot EPI had minimal intraslice phase discrepancies due to its small temporal footprint. Phase inconsistency between signal averages was well tolerated due to the high-pass filter effect of the SWI processing. Interleaved snapshot EPI with prospective and retrospective motion correction demonstrated similar image quality, regardless of whether motion was present. Lesion depiction was equal to 3D EPI with matching resolution. CONCLUSION Susceptibility-based imaging can be severely corrupted by head movement despite accurate prospective motion correction. Interleaved snapshot EPI is a superior alternative for patients who are prone to move and offers SWI which is insensitive to motion when combined with prospective and retrospective motion correction.
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Affiliation(s)
- Johan Berglund
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Tim Sprenger
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,MR Applied Science Laboratory, GE Healthcare, Stockholm, Sweden
| | - Adam van Niekerk
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Henric Rydén
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Enrico Avventi
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Ola Norbeck
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Stefan Skare
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
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13
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Sanchez Panchuelo RM, Mougin O, Turner R, Francis ST. Quantitative T1 mapping using multi-slice multi-shot inversion recovery EPI. Neuroimage 2021; 234:117976. [PMID: 33781969 PMCID: PMC8204273 DOI: 10.1016/j.neuroimage.2021.117976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 02/27/2021] [Accepted: 03/13/2021] [Indexed: 11/12/2022] Open
Abstract
An efficient multi-slice inversion–recovery EPI (MS-IR-EPI) sequence for fast, high spatial resolution, quantitative T1 mapping is presented, using a segmented simultaneous multi-slice acquisition, combined with slice order shifting across multiple acquisitions. The segmented acquisition minimises the effective TE and readout duration compared to a single-shot EPI scheme, reducing geometric distortions to provide high quality T1 maps with a narrow point-spread function. The precision and repeatability of MS-IR-EPI T1 measurements are assessed using both T1-calibrated and T2-calibrated ISMRM/NIST phantom spheres at 3 and 7 T and compared with single slice IR and MP2RAGE methods. Magnetization transfer (MT) effects of the spectrally-selective fat-suppression (FS) pulses required for in vivo imaging are shown to shorten the measured in-vivo T1 values. We model the effect of these fat suppression pulses on T1 measurements and show that the model can remove their MT contribution from the measured T1, thus providing accurate T1 quantification. High spatial resolution T1 maps of the human brain generated with MS-IR-EPI at 7 T are compared with those generated with the widely implemented MP2RAGE sequence. Our MS-IR-EPI sequence provides high SNR per unit time and sharper T1 maps than MP2RAGE, demonstrating the potential for ultra-high resolution T1 mapping and the improved discrimination of functionally relevant cortical areas in the human brain.
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Affiliation(s)
- Rosa M Sanchez Panchuelo
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom; NIHR Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, United Kingdom.
| | - Olivier Mougin
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom
| | - Robert Turner
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom; Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Susan T Francis
- Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom; NIHR Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, United Kingdom
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14
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Moia S, Termenon M, Uruñuela E, Chen G, Stickland RC, Bright MG, Caballero-Gaudes C. ICA-based denoising strategies in breath-hold induced cerebrovascular reactivity mapping with multi echo BOLD fMRI. Neuroimage 2021; 233:117914. [PMID: 33684602 PMCID: PMC8351526 DOI: 10.1016/j.neuroimage.2021.117914] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/25/2021] [Accepted: 02/22/2021] [Indexed: 12/19/2022] Open
Abstract
Performing a BOLD functional MRI (fMRI) acquisition during breath-hold (BH) tasks is a non-invasive, robust method to estimate cerebrovascular reactivity (CVR). However, movement and breathing-related artefacts caused by the BH can substantially hinder CVR estimates due to their high temporal collinearity with the effect of interest, and attention has to be paid when choosing which analysis model should be applied to the data. In this study, we evaluate the performance of multiple analysis strategies based on lagged general linear models applied on multi-echo BOLD fMRI data, acquired in ten subjects performing a BH task during ten sessions, to obtain subject-specific CVR and haemodynamic lag estimates. The evaluated approaches range from conventional regression models, i.e. including drifts and motion timecourses as nuisance regressors, applied on single-echo or optimally-combined data, to more complex models including regressors obtained from multi-echo independent component analysis with different grades of orthogonalization in order to preserve the effect of interest, i.e. the CVR. We compare these models in terms of their ability to make signal intensity changes independent from motion, as well as the reliability as measured by voxelwise intraclass correlation coefficients of both CVR and lag maps over time. Our results reveal that a conservative independent component analysis model applied on the optimally-combined multi-echo fMRI signal offers the largest reduction of motion-related effects in the signal, while yielding reliable CVR amplitude and lag estimates, although a conventional regression model applied on the optimally-combined data results in similar estimates. This work demonstrates the usefulness of multi-echo based fMRI acquisitions and independent component analysis denoising for precision mapping of CVR in single subjects based on BH paradigms, fostering its potential as a clinically-viable neuroimaging tool for individual patients. It also proves that the way in which data-driven regressors should be incorporated in the analysis model is not straight-forward due to their complex interaction with the BH-induced BOLD response.
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Affiliation(s)
- Stefano Moia
- Basque Center on Cognition, Brain and Language, Donostia, Spain; University of the Basque Country UPV/EHU, Donostia, Spain.
| | - Maite Termenon
- Basque Center on Cognition, Brain and Language, Donostia, Spain
| | - Eneko Uruñuela
- Basque Center on Cognition, Brain and Language, Donostia, Spain; University of the Basque Country UPV/EHU, Donostia, Spain
| | - Gang Chen
- Scientific and Statistical Computing Core, NIMH/NIH/HHS, Bethesda, MD, United States
| | - Rachael C Stickland
- Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Molly G Bright
- Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States; Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, IL, United States
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15
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An H, Shin HG, Ji S, Jung W, Oh S, Shin D, Park J, Lee J. DeepResp: Deep learning solution for respiration-induced B 0 fluctuation artifacts in multi-slice GRE. Neuroimage 2020; 224:117432. [PMID: 33038539 DOI: 10.1016/j.neuroimage.2020.117432] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 09/23/2020] [Accepted: 09/30/2020] [Indexed: 11/25/2022] Open
Abstract
Respiration-induced B0 fluctuation corrupts MRI images by inducing phase errors in k-space. A few approaches such as navigator have been proposed to correct for the artifacts at the expense of sequence modification. In this study, a new deep learning method, which is referred to as DeepResp, is proposed for reducing the respiration-artifacts in multi-slice gradient echo (GRE) images. DeepResp is designed to extract the respiration-induced phase errors from a complex image using deep neural networks. Then, the network-generated phase errors are applied to the k-space data, creating an artifact-corrected image. For network training, the computer-simulated images were generated using artifact-free images and respiration data. When evaluated, both simulated images and in-vivo images of two different breathing conditions (deep breathing and natural breathing) show improvements (simulation: normalized root-mean-square error (NRMSE) from 7.8 ± 5.2% to 1.3 ± 0.6%; structural similarity (SSIM) from 0.88 ± 0.08 to 0.99 ± 0.01; ghost-to-signal-ratio (GSR) from 7.9 ± 7.2% to 0.6 ± 0.6%; deep breathing: NRMSE from 13.9 ± 4.6% to 5.8 ± 1.4%; SSIM from 0.86 ± 0.03 to 0.95 ± 0.01; GSR 20.2 ± 10.2% to 5.7 ± 2.3%; natural breathing: NRMSE from 5.2 ± 3.3% to 4.0 ± 2.5%; SSIM from 0.94 ± 0.04 to 0.97 ± 0.02; GSR 5.7 ± 5.0% to 2.8 ± 1.1%). Our approach does not require any modification of the sequence or additional hardware, and may therefore find useful applications. Furthermore, the deep neural networks extract respiration-induced phase errors, which is more interpretable and reliable than results of end-to-end trained networks.
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Affiliation(s)
- Hongjun An
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Hyeong-Geol Shin
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Sooyeon Ji
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Woojin Jung
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Sehong Oh
- Division of Biomedical Engineering, Hankuk University of Foreign Studies, Gyeonggi-do, South Korea
| | - Dongmyung Shin
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Juhyung Park
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea
| | - Jongho Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, South Korea.
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16
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Simultaneous feedback control for joint field and motion correction in brain MRI. Neuroimage 2020; 226:117286. [PMID: 32992003 DOI: 10.1016/j.neuroimage.2020.117286] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/21/2020] [Accepted: 08/14/2020] [Indexed: 11/23/2022] Open
Abstract
T2*-weighted gradient-echo sequences count among the most widely used techniques in neuroimaging and offer rich magnitude and phase contrast. The susceptibility effects underlying this contrast scale with B0, making T2*-weighted imaging particularly interesting at high field. High field also benefits baseline sensitivity and thus facilitates high-resolution studies. However, enhanced susceptibility effects and high target resolution come with inherent challenges. Relying on long echo times, T2*-weighted imaging not only benefits from enhanced local susceptibility effects but also suffers from increased field fluctuations due to moving body parts and breathing. High resolution, in turn, renders neuroimaging particularly vulnerable to motion of the head. This work reports the implementation and characterization of a system that aims to jointly address these issues. It is based on the simultaneous operation of two control loops, one for field stabilization and one for motion correction. The key challenge with this approach is that the two loops both operate on the magnetic field in the imaging volume and are thus prone to mutual interference and potential instability. This issue is addressed at the levels of sensing, timing, and control parameters. Performance assessment shows the resulting system to be stable and exhibit adequate loop decoupling, precision, and bandwidth. Simultaneous field and motion control is then demonstrated in examples of T2*-weighted in vivo imaging at 7T.
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17
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Le Ster C, Mauconduit F, Mirkes C, Bottlaender M, Boumezbeur F, Djemai B, Vignaud A, Boulant N. RF heating measurement using MR thermometry and field monitoring: Methodological considerations and first in vivo results. Magn Reson Med 2020; 85:1282-1293. [PMID: 32936510 DOI: 10.1002/mrm.28501] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 07/10/2020] [Accepted: 08/10/2020] [Indexed: 11/11/2022]
Abstract
PURPOSE A MR thermometry (MRT) method with field monitoring is proposed to improve the measurement of small temperature variations induced in brain MRI exams. METHODS MR thermometry experiments were performed at 7 Tesla with concurrent field monitoring and RF heating. Images were reconstructed with nominal k-space trajectories and with first-order spherical harmonics correction. Experiments were performed in vitro with deliberate field disturbances and on an anesthetized macaque in 2 different specific absorption rate regimes, that is, at 50% and 100% of the maximal specific absorption rate level allowed in the International Electrotechnical Commission normal mode of operation. Repeatability was assessed by running a second separate session on the same animal. RESULTS Inclusion of magnetic field fluctuations in the reconstruction improved temperature measurement accuracy in vitro down to 0.02°C. Measurement precision in vivo was on the order of 0.15°C in areas little affected by motion. In the same region, temperature increase reached 0.5 to 0.8°C after 20 min of heating at 100% specific absorption rates and followed a rough factor of 2 with the 50% specific absorption rate scans. A horizontal temperature plateau, as predicted by Pennes bioheat model with thermal constants from the literature and constant blood temperature assumption, was not observed. CONCLUSION Inclusion of field fluctuations in image reconstruction was beneficial for the measurement of small temperature rises encountered in standard brain exams. More work is needed to correct for motion-induced field disturbances to extract reliable temperature maps.
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Affiliation(s)
- Caroline Le Ster
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Franck Mauconduit
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | | | - Michel Bottlaender
- Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Service Hospitalier Frederic Joliot, Orsay, France.,UNIACT, Neurospin, CEA, Gif-sur-Yvette, France
| | - Fawzi Boumezbeur
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Boucif Djemai
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Alexandre Vignaud
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
| | - Nicolas Boulant
- Université Paris-Saclay, CEA, CNRS, BAOBAB, NeuroSpin, Gif-sur-Yvette, France
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18
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Bazin PL, Nijsse HE, van der Zwaag W, Gallichan D, Alkemade A, Vos FM, Forstmann BU, Caan MWA. Sharpness in motion corrected quantitative imaging at 7T. Neuroimage 2020; 222:117227. [PMID: 32781231 DOI: 10.1016/j.neuroimage.2020.117227] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 07/03/2020] [Accepted: 07/31/2020] [Indexed: 12/13/2022] Open
Abstract
Sub-millimeter imaging at 7T has opened new possibilities for qualitatively and quantitatively studying brain structure as it evolves throughout the life span. However, subject motion introduces image blurring on the order of magnitude of the spatial resolution and is thus detrimental to image quality. Such motion can be corrected for, but widespread application has not yet been achieved and quantitative evaluation is lacking. This raises a need to quantitatively measure image sharpness throughout the brain. We propose a method to quantify sharpness of brain structures at sub-voxel resolution, and use it to assess to what extent limited motion is related to image sharpness. The method was evaluated in a cohort of 24 healthy volunteers with a wide and uniform age range, aiming to arrive at results that largely generalize to larger populations. Using 3D fat-excited motion navigators, quantitative R1, R2* and Quantitative Susceptibility Maps and T1-weighted images were retrospectively corrected for motion. Sharpness was quantified in all modalities for selected regions of interest (ROI) by fitting the sigmoidally shaped error function to data within locally homogeneous clusters. A strong, almost linear correlation between motion and sharpness improvement was observed, and motion correction significantly improved sharpness. Overall, the Full Width at Half Maximum reduced from 0.88 mm to 0.70 mm after motion correction, equivalent to a 2.0 times smaller voxel volume. Motion and sharpness were not found to correlate with the age of study participants. We conclude that in our data, motion correction using fat navigators is overall able to restore the measured sharpness to the imaging resolution, irrespective of the amount of motion observed during scanning.
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Affiliation(s)
- Pierre-Louis Bazin
- Integrative Model-based Cognitive Neuroscience research unit, Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands.
| | - Hannah E Nijsse
- Department of Imaging Physics, Delft University of Technology, Delft, the Netherlands.
| | | | - Daniel Gallichan
- CUBRIC, School of Engineering, Cardiff University, Cardiff, United Kingdom.
| | - Anneke Alkemade
- Integrative Model-based Cognitive Neuroscience research unit, Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands.
| | - Frans M Vos
- Department of Imaging Physics, Delft University of Technology, Delft, the Netherlands.
| | - Birte U Forstmann
- Integrative Model-based Cognitive Neuroscience research unit, Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands.
| | - Matthan W A Caan
- Amsterdam UMC, University of Amsterdam, Biomedical Engineering and Physics, Amsterdam, the Netherlands.
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19
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DiGiacomo P, Maclaren J, Aksoy M, Tong E, Carlson M, Lanzman B, Hashmi S, Watkins R, Rosenberg J, Burns B, Skloss TW, Rettmann D, Rutt B, Bammer R, Zeineh M. A within-coil optical prospective motion-correction system for brain imaging at 7T. Magn Reson Med 2020; 84:1661-1671. [PMID: 32077521 DOI: 10.1002/mrm.28211] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 01/18/2020] [Accepted: 01/21/2020] [Indexed: 12/22/2022]
Abstract
PURPOSE Motion artifact limits the clinical translation of high-field MR. We present an optical prospective motion correction system for 7 Tesla MRI using a custom-built, within-coil camera to track an optical marker mounted on a subject. METHODS The camera was constructed to fit between the transmit-receive coils with direct line of sight to a forehead-mounted marker, improving upon prior mouthpiece work at 7 Tesla MRI. We validated the system by acquiring a 3D-IR-FSPGR on a phantom with deliberate motion applied. The same 3D-IR-FSPGR and a 2D gradient echo were then acquired on 7 volunteers, with/without deliberate motion and with/without motion correction. Three neuroradiologists blindly assessed image quality. In 1 subject, an ultrahigh-resolution 2D gradient echo with 4 averages was acquired with motion correction. Four single-average acquisitions were then acquired serially, with the subject allowed to move between acquisitions. A fifth single-average 2D gradient echo was acquired following subject removal and reentry. RESULTS In both the phantom and human subjects, deliberate and involuntary motion were well corrected. Despite marked levels of motion, high-quality images were produced without spurious artifacts. The quantitative ratings confirmed significant improvements in image quality in the absence and presence of deliberate motion across both acquisitions (P < .001). The system enabled ultrahigh-resolution visualization of the hippocampus during a long scan and robust alignment of serially acquired scans with interspersed movement. CONCLUSION We demonstrate the use of a within-coil camera to perform optical prospective motion correction and ultrahigh-resolution imaging at 7 Tesla MRI. The setup does not require a mouthpiece, which could improve accessibility of motion correction during 7 Tesla MRI exams.
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Affiliation(s)
- Phillip DiGiacomo
- Department of Bioengineering, Stanford University, Stanford, California
| | - Julian Maclaren
- Department of Radiology, Stanford University, Stanford, California
| | - Murat Aksoy
- Department of Radiology, Stanford University, Stanford, California
| | - Elizabeth Tong
- Department of Radiology, Stanford University, Stanford, California
| | - Mackenzie Carlson
- Department of Bioengineering, Stanford University, Stanford, California
| | - Bryan Lanzman
- Department of Radiology, Stanford University, Stanford, California
| | - Syed Hashmi
- Department of Radiology, Stanford University, Stanford, California
| | - Ronald Watkins
- Department of Radiology, Stanford University, Stanford, California
| | | | - Brian Burns
- Applied Sciences Lab West, GE Healthcare, Menlo Park, California
| | | | - Dan Rettmann
- MR Applications and Workflow, GE Healthcare, Rochester, Minnesota
| | - Brian Rutt
- Department of Bioengineering, Stanford University, Stanford, California.,Department of Radiology, Stanford University, Stanford, California
| | - Roland Bammer
- Department of Radiology, University of Melbourne, Melbourne, Australia
| | - Michael Zeineh
- Department of Radiology, Stanford University, Stanford, California
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20
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Romero JA, Rodriguez GG, Anoardo E. A fast field-cycling MRI relaxometer for physical contrasts design and pre-clinical studies in small animals. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2020; 311:106682. [PMID: 31923764 DOI: 10.1016/j.jmr.2019.106682] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 12/28/2019] [Accepted: 12/29/2019] [Indexed: 06/10/2023]
Abstract
We present a fast field-cycling NMR relaxometer with added magnetic resonance imaging capabilities. The instrument operates at a maximum proton Larmor frequency of 5 MHz for a sample volume of 35 mL. The magnetic field homogeneity across the sample is 1400 ppm. The main field is generated with a notch-coil electromagnet of own design, fed with a current whose stability is 220 ppm. We show that images of reasonable quality can still be produced under such conditions. The machine is being designed for concept testing of the involved instrumentation and specific contrast agents aimed for field-cycling magnetic resonance imaging applications. The general performance of the prototype was tested through localized relaxometry experiments, T1-dispersion weighted images, temperature maps and T1-weighted images at different magnetic field intensities. We introduce the concept of positive and negative contrast depending on the use of pre-polarized or non-polarized sequences. The system is being improved for pre-clinical studies in small animals.
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Affiliation(s)
- Javier A Romero
- Laboratorio de Relaxometría y Técnicas Especiales (LaRTE), Grupo de Resonancia Magnética Nuclear, FaMAF, Universidad Nacional de Córdoba e IFEG-CONICET, Córdoba, Argentina
| | - Gonzalo G Rodriguez
- Laboratorio de Relaxometría y Técnicas Especiales (LaRTE), Grupo de Resonancia Magnética Nuclear, FaMAF, Universidad Nacional de Córdoba e IFEG-CONICET, Córdoba, Argentina
| | - Esteban Anoardo
- Laboratorio de Relaxometría y Técnicas Especiales (LaRTE), Grupo de Resonancia Magnética Nuclear, FaMAF, Universidad Nacional de Córdoba e IFEG-CONICET, Córdoba, Argentina.
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21
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Liu J, van Gelderen P, de Zwart JA, Duyn JH. Reducing motion sensitivity in 3D high-resolution T 2*-weighted MRI by navigator-based motion and nonlinear magnetic field correction. Neuroimage 2019; 206:116332. [PMID: 31689535 DOI: 10.1016/j.neuroimage.2019.116332] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 10/24/2019] [Accepted: 11/01/2019] [Indexed: 02/08/2023] Open
Abstract
T2*-weighted gradient echo (GRE) MRI at high field is uniquely sensitive to the magnetic properties of tissue and allows the study of brain and vascular anatomy at high spatial resolution. However, it is also sensitive to B0 field changes induced by head motion and physiological processes such as the respiratory cycle. Conventional motion correction techniques do not take these field changes into account, and consequently do not fully recover image quality in T2*-weighted MRI. Here, a novel approach was developed to address this by monitoring the B0 field with a volumetric EPI phase navigator. The navigator was acquired at a shorter echo time than that of the (higher resolution) T2*-weighted GRE imaging data and accelerated with parallel imaging for high temporal resolution. At 4 mm isotropic spatial resolution and 0.54 s temporal resolution, the accuracy for estimation of rotation and translation was better than 0.2° and 0.1 mm, respectively. The 10% and 90% percentiles of B0 measurement error using the navigator were -1.8 and 1.5 Hz at 7 T, respectively. A fast retrospective reconstruction algorithm correcting for both motion and nonlinear B0 changes was also developed. The navigator and reconstruction algorithm were evaluated in correcting motion-corrupted high-resolution T2*-weighted GRE MRI on healthy human subjects at 7 T. Excellent image quality was demonstrated with the proposed correction method.
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Affiliation(s)
- Jiaen Liu
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Dr. BLDG. 10, RM. B1D-723, Bethesda, MD, 20892-1065, USA.
| | - Peter van Gelderen
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Dr. BLDG. 10, RM. B1D-723, Bethesda, MD, 20892-1065, USA
| | - Jacco A de Zwart
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Dr. BLDG. 10, RM. B1D-723, Bethesda, MD, 20892-1065, USA
| | - Jeff H Duyn
- Advanced MRI Section, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Dr. BLDG. 10, RM. B1D-723, Bethesda, MD, 20892-1065, USA
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22
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Vannesjo SJ, Clare S, Kasper L, Tracey I, Miller KL. A method for correcting breathing-induced field fluctuations in T2*-weighted spinal cord imaging using a respiratory trace. Magn Reson Med 2019; 81:3745-3753. [PMID: 30737825 PMCID: PMC6492127 DOI: 10.1002/mrm.27664] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 12/01/2018] [Accepted: 12/27/2018] [Indexed: 02/04/2023]
Abstract
PURPOSE Spinal cord MRI at ultrahigh field is hampered by time-varying magnetic fields associated with the breathing cycle, giving rise to ghosting artifacts in multi-shot acquisitions. Here, we suggest a correction approach based on linking the signal from a respiratory bellows to field changes inside the spinal cord. The information is used to correct the data at the image reconstruction level. METHODS The correction was demonstrated in the context of multi-shot T2*-weighted imaging of the cervical spinal cord at 7T. A respiratory trace was acquired during a high-resolution multi-echo gradient-echo sequence, used for structural imaging and quantitative T2* mapping, and a multi-shot EPI time series, as would be suitable for fMRI. The coupling between the trace and the breathing-induced fields was determined by a short calibration scan in each individual. Images were reconstructed with and without trace-based correction. RESULTS In the multi-echo acquisition, breathing-induced fields caused severe ghosting in images with long TE, which led to a systematic underestimation of T2* in the spinal cord. The trace-based correction reduced the ghosting and increased the estimated T2* values. Breathing-related ghosting was also observed in the multi-shot EPI images. The correction largely removed the ghosting, thereby improving the temporal signal-to-noise ratio of the time series. CONCLUSIONS Trace-based retrospective correction of breathing-induced field variations can reduce ghosting and improve quantitative metrics in multi-shot structural and functional T2*-weighted imaging of the spinal cord. The method is straightforward to implement and does not rely on sequence modifications or additional hardware beyond a respiratory bellows.
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Affiliation(s)
- S. Johanna Vannesjo
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
| | - Stuart Clare
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
| | - Lars Kasper
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurichSwitzerland
- Translational Neuromodeling Unit, Institute for Biomedical EngineeringUniversity of Zurich and ETH ZurichZurichSwitzerland
| | - Irene Tracey
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
| | - Karla L. Miller
- Wellcome Centre for Integrative Neuroimaging, FMRIB, Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
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23
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Choi JY, Lee J, Nam Y, Lee J, Oh SH. Improvement of reproducibility in quantitative susceptibility mapping (QSM) and transverse relaxation rates ( R 2 * ) after physiological noise correction. J Magn Reson Imaging 2019; 49:1769-1776. [PMID: 31062456 DOI: 10.1002/jmri.26522] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 09/06/2018] [Accepted: 09/07/2018] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND Numerous studies have suggested that quantitative susceptibility mapping (QSM) and transverse relaxation rates ( R 2 * ) are useful to monitor neurological diseases. For clinical use of QSM and R 2 * , reproducibility is an important feature. However, respiration-induced local magnetic field variation makes artifacts in gradient echo-based images and reduces the reproducibility of QSM and R 2 * . PURPOSE To investigate the improvement of reproducibility of QSM and R 2 * after the correction of respiration-induced field variation, and to assess the effect of varying types of the region of interest (ROI) analysis on reproducibility. STUDY TYPE Reproducibility study. POPULATION Ten controls. FIELD STRENGTH/SEQUENCE 3T/multiecho gradient echo sequence. ASSESSMENT Intrascan reproducibility of QSM and R 2 * was investigated in ROIs before and after the respiration correction. STATISTICAL TESTS Reproducibility was obtained by the square of voxel-wise correlation coefficients between scans. A paired t-test was performed for comparison between before and after the respiration correction and between QSM and R 2 * . RESULTS Based on the ROI analysis, reproducibility increased after the respiration correction. Reproducibility in the white matter (11.89% increased in QSM and 23.38% in R 2 * , P = 0.009 and 0.024, respectively) and deep gray matter (5.50% increased in QSM and 13.96% in R 2 * , P = 0.024 and 0.019, respectively) increased significantly after the respiration correction. Reproducibility of R 2 * was higher than that of QSM in the whole brain and cortical gray matter, while QSM maps showed higher reproducibility than R 2 * in the white matter and deep gray matter. DATA CONCLUSION Respiration-induced error correction significantly improved reproducibility in QSM and R 2 * mapping. QSM and R 2 * mapping showed a different level of reproducibility depending on the types of ROI analysis. LEVEL OF EVIDENCE 4 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018.
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Affiliation(s)
- Joon Yul Choi
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Jingu Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Yoonho Nam
- Department of Radiology, Seoul Saint Mary's Hospital, College of Medicine, Catholic University of Korea, Seoul, Republic of Korea
| | - Jongho Lee
- Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea
| | - Se-Hong Oh
- Division of Biomedical Engineering, Hankuk University of Foreign Studies, Gyeonggi-do, Republic of Korea
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24
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SPARKLING: variable-density k-space filling curves for accelerated T2
*
-weighted MRI. Magn Reson Med 2019; 81:3643-3661. [DOI: 10.1002/mrm.27678] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 12/18/2018] [Accepted: 01/08/2019] [Indexed: 01/25/2023]
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25
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Meineke J, Nielsen T. Data consistency-driven determination of B 0 -fluctuations in gradient-echo MRI. Magn Reson Med 2018; 81:3046-3055. [PMID: 30515876 DOI: 10.1002/mrm.27630] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 11/15/2018] [Accepted: 11/15/2018] [Indexed: 01/26/2023]
Abstract
PURPOSE Introduce a method to estimate B 0 -fluctuations based on the analysis of raw k-space data, without sequence modifications or external hardware, and correct for their detrimental effects in gradient-echo MRI. THEORY Inconsistencies in multi-channel raw k-space data can be used to estimate B 0 -fluctuations by exploiting coil-sensitivity information. METHODS The proposed method, dubbed consistency navigation, is used to extract B 0 -fluctuations from T 2 * -weighted 3D gradient-echo data. These results are compared with the results from an MR phase navigator and respiratory bellows. The spatial variation of the B 0 -fluctuation amplitude is derived using the sensitivity maps of the coil array and compared with direct measurements based on dynamic 2D gradient-echo data. RESULTS B 0 -fluctuations derived from the consistency navigator and MR phase navigator are highly correlated. Images corrected for these fluctuations show marked improvements in homogeneity and tissue delineation. The spatial variation of the B 0 -fluctuation amplitude follows closely the variation directly measured from time-resolved 2D scans. CONCLUSIONS Based on the consistency navigator, an accurate estimation of the spatiotemporal characteristics of B 0 -fluctuations and correction of T 2 * -weighted images has been demonstrated.
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26
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Magnetic Resonance Imaging technology-bridging the gap between noninvasive human imaging and optical microscopy. Curr Opin Neurobiol 2018; 50:250-260. [PMID: 29753942 DOI: 10.1016/j.conb.2018.04.026] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 04/20/2018] [Accepted: 04/24/2018] [Indexed: 12/23/2022]
Abstract
Technological advances in Magnetic Resonance Imaging (MRI) have provided substantial gains in the sensitivity and specificity of functional neuroimaging. Mounting evidence demonstrates that the hemodynamic changes utilized in functional MRI can be far more spatially and thus neuronally specific than previously believed. This has motivated a push toward novel, high-resolution MR imaging strategies that can match this biological resolution limit while recording from the entire human brain. Although sensitivity increases are a necessary component, new MR encoding technologies are required to convert improved sensitivity into higher resolution. These new sampling strategies improve image acquisition efficiency and enable increased image encoding in the time-frame needed to follow hemodynamic changes associated with brain activation.
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27
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Engel M, Kasper L, Barmet C, Schmid T, Vionnet L, Wilm B, Pruessmann KP. Single‐shot spiral imaging at 7
T. Magn Reson Med 2018; 80:1836-1846. [DOI: 10.1002/mrm.27176] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 02/15/2018] [Accepted: 02/18/2018] [Indexed: 01/18/2023]
Affiliation(s)
- Maria Engel
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
| | - Lars Kasper
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
- Translational Neuromodeling Unit, Institute for Biomedical EngineeringUniversity of Zurich and ETH ZurichZurich Switzerland
| | - Christoph Barmet
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
- Skope Magnetic Resonance Technologies AGZurich Switzerland
| | - Thomas Schmid
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
| | - Laetitia Vionnet
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
| | - Bertram Wilm
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
- Skope Magnetic Resonance Technologies AGZurich Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical EngineeringETH Zurich and University of ZurichZurich Switzerland
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28
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Barry RL, Vannesjo SJ, By S, Gore JC, Smith SA. Spinal cord MRI at 7T. Neuroimage 2018; 168:437-451. [PMID: 28684332 PMCID: PMC5894871 DOI: 10.1016/j.neuroimage.2017.07.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 06/30/2017] [Accepted: 07/02/2017] [Indexed: 11/25/2022] Open
Abstract
Magnetic resonance imaging (MRI) of the human spinal cord at 7T has been demonstrated by a handful of research sites worldwide, and the spinal cord remains one of the areas in which higher fields and resolution could have high impact. The small diameter of the cord (∼1 cm) necessitates high spatial resolution to minimize partial volume effects between gray and white matter, and so MRI of the cord can greatly benefit from increased signal-to-noise ratio and contrasts at ultra-high field (UHF). Herein we review the current state of UHF spinal cord imaging. Technical challenges to successful UHF spinal cord MRI include radiofrequency (B1) nonuniformities and a general lack of optimized radiofrequency coils, amplified physiological noise, and an absence of methods for robust B0 shimming along the cord to mitigate image distortions and signal losses. Numerous solutions to address these challenges have been and are continuing to be explored, and include novel approaches for signal excitation and acquisition, dynamic shimming and specialized shim coils, and acquisitions with increased coverage or optimal slice angulations.
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Affiliation(s)
- Robert L Barry
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA; Department of Radiology, Harvard Medical School, Boston, MA, USA.
| | - S Johanna Vannesjo
- Oxford Centre for Functional MRI of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Samantha By
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - John C Gore
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Seth A Smith
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, USA; Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
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29
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How to choose the right MR sequence for your research question at 7 T and above? Neuroimage 2018; 168:119-140. [DOI: 10.1016/j.neuroimage.2017.04.044] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 04/18/2017] [Accepted: 04/19/2017] [Indexed: 12/29/2022] Open
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30
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Looser A, Barmet C, Fox T, Blacque O, Gross S, Nussbaum J, Pruessmann KP, Alberto R. Ultrafast Ligand Self-Exchanging Gadolinium Complexes in Ionic Liquids for NMR Field Probes. Inorg Chem 2018; 57:2314-2319. [DOI: 10.1021/acs.inorgchem.7b03191] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anna Looser
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Christoph Barmet
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
- Skope Magnetic Resonance Technologies AG, Gladbachstrasse 105, CH-8044 Zurich, Switzerland
| | - Thomas Fox
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Olivier Blacque
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Simon Gross
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Jennifer Nussbaum
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Klaas P. Pruessmann
- Institute
for Biomedical Engineering, ETH Zurich and University of Zurich, Gloriastrasse 35, CH-8092 Zurich, Switzerland
| | - Roger Alberto
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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31
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Topfer R, Foias A, Stikov N, Cohen-Adad J. Real-time correction of respiration-induced distortions in the human spinal cord using a 24-channel shim array. Magn Reson Med 2018; 80:935-946. [DOI: 10.1002/mrm.27089] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 12/22/2017] [Accepted: 12/24/2017] [Indexed: 12/25/2022]
Affiliation(s)
- Ryan Topfer
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
| | - Alexandru Foias
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
| | - Nikola Stikov
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
- Montreal Heart Institute, Université de Montréal; Montreal Quebec Canada
| | - Julien Cohen-Adad
- NeuroPoly Lab, Institute of Biomedical Engineering, Polytechnique Montreal; Montreal Quebec Canada
- Functional Neuroimaging Unit, CRIUGM, Université de Montréal; Montreal Quebec Canada
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32
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Gretsch F, Marques JP, Gallichan D. Investigating the accuracy of FatNav-derived estimates of temporal B 0 changes and their application to retrospective correction of high-resolution 3D GRE of the human brain at 7T. Magn Reson Med 2018; 80:585-597. [PMID: 29359352 DOI: 10.1002/mrm.27063] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 11/30/2017] [Accepted: 12/06/2017] [Indexed: 11/05/2022]
Abstract
PURPOSE To investigate the precision of estimates of temporal variations of magnetic field achievable by double-echo fat image navigators (FatNavs), and their potential application to retrospective correction of 3-dimensional gradient echo-based sequences. METHODS Both head motion and temporal changes of B0 were tracked using double-echo highly accelerated 3-dimensional FatNavs as navigators, allowing estimation of the temporal changes in low spatial-order field coefficients. The accuracy of the method was determined by direct comparison to controlled offsets in the linear imaging gradients. Double-echo FatNavs were also incorporated into a high-resolution, 3-dimensional gradient echo-based sequence to retrospectively correct for both motion and temporal changes in B0 during natural and deep breathing. The additional scan time was 5 min (a 40% increase). Correction was also investigated using only the first echo of the FatNav to explore the trade-off in accuracy versus scan time. RESULTS Excellent accuracy (0.27 Hz, 1.57-2.75 Hz/m) was achieved for tracking field changes, and no significant bias could be observed. Artifacts in the 3-dimensional gradient echo-based images induced by temporal field changes, if present, were effectively reduced using either the field estimates from the double echo or the first echo only from the FatNavs. CONCLUSION The FatNavs were shown to be an excellent candidate for accurate, fast, and precise estimation of global field variations for the tested patterns of respiration. Future work will investigate ways to increase the temporal sampling to increase robustness to variations in breathing patterns. Magn Reson Med 80:585-597, 2018. © 2018 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Frédéric Gretsch
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - José P Marques
- Donders Institute, Radboud University, Nijmegen, the Netherlands
| | - Daniel Gallichan
- Biomedical Imaging Research Center, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,Cardiff University Brain Research Imaging Centre (CUBRIC), School of Engineering, Cardiff University, Cardiff, United Kingdom
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Kennedy M, Lee Y, Nagy Z. An industrial design solution for integrating NMR magnetic field sensors into an MRI scanner. Magn Reson Med 2017; 80:833-839. [PMID: 29285786 DOI: 10.1002/mrm.27055] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 11/30/2017] [Accepted: 12/01/2017] [Indexed: 11/09/2022]
Abstract
PURPOSE Neuroimaging research relies on the skills of increasingly multidisciplinary individuals and often requires the installation and use of additional home-built or third-party equipment. The purpose of the present work was the safe, ergonomic, durable, and aesthetically pleasing installation of magnetic field monitoring equipment into a scanner, while keeping the setup compatible with standard operating procedures. METHODS An extensive set of steps was required to design a 3D printed solution to install a magnetic field camera into the eight-channel head coil of a 3T MRI scanner. First, the outer surface of the plastic coil housing was recreated into a 3D model, and the installation of the magnetic field sensors around this 3D model was performed in a virtual environment. The 3D printed solution was then assembled and tested for safety, reproducible performance, and image quality. RESULTS The 3D printed solution holds the probes in stable positions and guides the necessary cables in an organized fashion and away from the volunteer. Assembly is easy and the solution is ergonomic, durable, and safe. We did not find excessive heating in the 3D printed parts, nor in the electronics, that they help to incorporate. The material used interferes minimally with transmit B1+ field. CONCLUSION The design met all of the boundary conditions for a durable, safe, cost-effective, attractive, and functional installation. This work will provide the basis for installing the magnetic field sensors into other available head coils, and for designing the experimental setup for projects with varying experimental requirements. Magn Reson Med 80:833-839, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Michael Kennedy
- Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland.,Department of Design, Industrial Design Unit, Zurich University of the Arts, Zurich, Switzerland
| | - Yoojin Lee
- Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland.,Institute of Biomedical Engineering, ETH, Zurich, Switzerland
| | - Zoltan Nagy
- Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland.,Institute of Biomedical Engineering, ETH, Zurich, Switzerland
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Spatiotemporal characterization of breathing-induced B 0 field fluctuations in the cervical spinal cord at 7T. Neuroimage 2017; 167:191-202. [PMID: 29175497 PMCID: PMC5854299 DOI: 10.1016/j.neuroimage.2017.11.031] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 10/09/2017] [Accepted: 11/15/2017] [Indexed: 01/31/2023] Open
Abstract
Magnetic resonance imaging and spectroscopy of the spinal cord stand to benefit greatly from the increased signal-to-noise ratio of ultra-high field. However, ultra-high field also poses considerable technical challenges, especially related to static and dynamic B0 fields. Breathing causes the field to fluctuate with the respiratory cycle, giving rise to artifacts such as ghosting and apparent motion in images. We here investigated the spatial and temporal characteristics of breathing-induced B0 fields in the cervical spinal cord at 7T. We analyzed the magnitude and spatial profile of breathing-induced fields during breath-holds in an expired and inspired breathing state. We also measured the temporal field evolution during free breathing by acquiring a time series of fast phase images, and a principal component analysis was performed on the measured field evolution. In all subjects, the field shift was largest around the vertebral level of C7 and lowest at the top of the spinal cord. At C7, we measured peak-to-peak field fluctuations of 36 Hz on average during normal free breathing; increasing to on average 113 Hz during deep breathing. The first principal component could explain more than 90% of the field variations along the foot-head axis inside the spinal cord in all subjects. We further implemented a proof-of-principle shim correction, demonstrating the feasibility of using the shim system to compensate for the breathing-induced fields inside the spinal cord. Effective correction strategies will be crucial to unlock the full potential of ultra-high field for spinal cord imaging. The B0 field in the spinal cord fluctuates with the breathing cycle. Average peak-to-peak ΔB0 of 36/113 Hz at C7 during normal/deep breathing at 7T. The first principal component explains more than 90% of the field variance. Respiratory trace correlates well with field fluctuations during normal breathing. Proof-of-principle correction using 2nd-order shims was demonstrated.
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35
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Serial correlations in single-subject fMRI with sub-second TR. Neuroimage 2017; 166:152-166. [PMID: 29066396 DOI: 10.1016/j.neuroimage.2017.10.043] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 10/16/2017] [Accepted: 10/20/2017] [Indexed: 01/29/2023] Open
Abstract
When performing statistical analysis of single-subject fMRI data, serial correlations need to be taken into account to allow for valid inference. Otherwise, the variability in the parameter estimates might be under-estimated resulting in increased false-positive rates. Serial correlations in fMRI data are commonly characterized in terms of a first-order autoregressive (AR) process and then removed via pre-whitening. The required noise model for the pre-whitening depends on a number of parameters, particularly the repetition time (TR). Here we investigate how the sub-second temporal resolution provided by simultaneous multislice (SMS) imaging changes the noise structure in fMRI time series. We fit a higher-order AR model and then estimate the optimal AR model order for a sequence with a TR of less than 600 ms providing whole brain coverage. We show that physiological noise modelling successfully reduces the required AR model order, but remaining serial correlations necessitate an advanced noise model. We conclude that commonly used noise models, such as the AR(1) model, are inadequate for modelling serial correlations in fMRI using sub-second TRs. Rather, physiological noise modelling in combination with advanced pre-whitening schemes enable valid inference in single-subject analysis using fast fMRI sequences.
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36
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Wyss M, Duerst Y, Nanz D, Kasper L, Wilm BJ, Dietrich BE, Gross S, Schmid T, Brunner DO, Pruessmann KP. Feedback field control improves the precision of T 2 * quantification at 7 T. NMR IN BIOMEDICINE 2017; 30:e3753. [PMID: 28678353 DOI: 10.1002/nbm.3753] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 04/10/2017] [Accepted: 05/04/2017] [Indexed: 06/07/2023]
Abstract
T2 * mapping offers access to a number of important structural and physiological tissue parameters. It is robust against RF field variations and overall signal scaling. However, T2 * measurement is highly sensitive to magnetic field errors, including perturbations caused by breathing motion at high baseline field. The goal of this work is to assess this issue in T2 * mapping of the brain and to study the benefit of field stabilization by feedback field control. T2 * quantification in the brain was investigated by phantom and in vivo measurements at 7 T. Repeated measurements were made with and without feedback field control using NMR field sensing and dynamic third-order shim actuation. The precision and reliability of T2 * quantification was assessed by studying variation across repeated measurements as well as fitting errors. Breathing effects were found to introduce significant error in T2 * mapping results. Field control mitigates this problem substantially. In a phantom it virtually eliminates the effects of emulated breathing fluctuations in the head. In vivo it enhances the structural fidelity of T2 * maps and reduces fitting residuals along with standard deviation. In conclusion, feedback field control improves the fidelity of T2 * mapping in the presence of field perturbations. It is an effective means of countering bulk susceptibility effects of breathing and hence holds particular promise for efforts to leverage high field for T2 * studies in vivo.
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Affiliation(s)
- Michael Wyss
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
| | - Yolanda Duerst
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
| | - Daniel Nanz
- University Hospital Zurich Institute of Diagnostic and Interventional Radiology, Zurich, Switzerland
| | - Lars Kasper
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
- University of Zurich and ETH Zurich Translational Neuromodeling Unit, Zurich, Switzerland
| | - Bertram Jakob Wilm
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
| | | | - Simon Gross
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
| | - Thomas Schmid
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
| | - David Otto Brunner
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
| | - Klaas Paul Pruessmann
- University of Zurich and ETH Zurich Institute for Biomedical Engineering, Zurich, Switzerland
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37
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Decoupled dynamic magnetic field measurements improves diffusion-weighted magnetic resonance images. Sci Rep 2017; 7:11630. [PMID: 28912538 PMCID: PMC5599543 DOI: 10.1038/s41598-017-11138-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 08/17/2017] [Indexed: 11/08/2022] Open
Abstract
Field probes are miniature receiver coils with localized NMR-active samples inside. They are useful in monitoring magnetic field. This information can be used to improve magnetic resonance image quality. While field probes are coupled to each other marginally in most applications, this coupling can cause incorrect resonance frequency estimates and image reconstruction errors. Here, we propose a method to reduce the coupling between field probes in order to improve the accuracy of magnetic field estimation. An asymmetric sensitivity matrix describing the coupling between channels of field probes and NMR active droplets within field probes was empirically measured. Localized signal originating from each probe was derived from the product of the inverse of the sensitivity matrix and the coupled probe measurements. This method was used to estimate maps of dynamic magnetic fields in diffusion weighted MRI. The estimated fields using decoupled probe measurement led to images more robust to eddy currents caused by diffusion sensitivity gradients along different directions.
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38
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Kasper L, Engel M, Barmet C, Haeberlin M, Wilm BJ, Dietrich BE, Schmid T, Gross S, Brunner DO, Stephan KE, Pruessmann KP. Rapid anatomical brain imaging using spiral acquisition and an expanded signal model. Neuroimage 2017; 168:88-100. [PMID: 28774650 DOI: 10.1016/j.neuroimage.2017.07.062] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Revised: 06/22/2017] [Accepted: 07/29/2017] [Indexed: 11/30/2022] Open
Abstract
We report the deployment of spiral acquisition for high-resolution structural imaging at 7T. Long spiral readouts are rendered manageable by an expanded signal model including static off-resonance and B0 dynamics along with k-space trajectories and coil sensitivity maps. Image reconstruction is accomplished by inversion of the signal model using an extension of the iterative non-Cartesian SENSE algorithm. Spiral readouts up to 25 ms are shown to permit whole-brain 2D imaging at 0.5 mm in-plane resolution in less than a minute. A range of options is explored, including proton-density and T2* contrast, acceleration by parallel imaging, different readout orientations, and the extraction of phase images. Results are shown to exhibit competitive image quality along with high geometric consistency.
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Affiliation(s)
- Lars Kasper
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland; Translational Neuromodeling Unit, IBT, University of Zurich and ETH Zurich, Zurich, Switzerland.
| | - Maria Engel
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Christoph Barmet
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland; Skope Magnetic Resonance Technologies AG, Zurich, Switzerland
| | - Maximilian Haeberlin
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Klaas E Stephan
- Translational Neuromodeling Unit, IBT, University of Zurich and ETH Zurich, Zurich, Switzerland; Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom; Max Planck Institute for Metabolism Research, Cologne, Germany
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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39
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Çavuşoğlu M, Mooiweer R, Pruessmann KP, Malik SJ. VERSE-guided parallel RF excitations using dynamic field correction. NMR IN BIOMEDICINE 2017; 30:e3697. [PMID: 28211968 PMCID: PMC5484370 DOI: 10.1002/nbm.3697] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 11/24/2016] [Accepted: 12/29/2016] [Indexed: 06/06/2023]
Abstract
In parallel RF pulse design, peak RF magnitudes and specific absorption rate levels are critical concerns in the hardware and safety limits. The variable rate selective excitation (VERSE) method is an efficient technique to limit the peak RF power by applying a local-only RF and gradient waveform reshaping while retaining the on-resonance profile. The accuracy of the excitation performed by the VERSEd RF and gradient waveforms strictly depends on the performance of the employed hardware. Any deviation from the nominal gradient fields as a result of frequency dependent system imperfections violates the VERSE condition similarly to off-resonance effects, leading to significant excitation errors and the RF pulse not converging to the targeted peak RF power. Moreover, for iterative VERSE-guided RF pulse design (i.e. reVERSE), the k-space trajectory actually changes at every iteration, which is assumed to be constant. In this work, we show both theoretically and experimentally the effect of gradient system imperfections on iteratively VERSEd parallel RF excitations. In order to improve the excitation accuracy besides limiting the RF power below certain thresholds, we propose to integrate gradient field monitoring or gradient impulse response function (GIRF) estimations of the actual gradient fields into the RF pulse design problem. A third-order dynamic field camera comprising a set of NMR field sensors and GIRFs was used to measure or estimate the actual gradient waveforms that are involved in the VERSE algorithm respectively. The deviating and variable k-space is counteracted at each iteration of the VERSE-guided iterative RF pulse design. The proposed approaches are demonstrated for accelerated multiple-channel spatially selective RF pulses, and highly improved experimental performance was achieved at both 3 T and 7 T.
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Affiliation(s)
- Mustafa Çavuşoğlu
- Institute for Biomedical EngineeringUniversity and ETH ZürichZürichSwitzerland
| | - Ronald Mooiweer
- Division of Imaging Sciences and Biomedical Engineering, King's College LondonSt. Thomas' HospitalLondonUK
- Center for Image SciencesUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Klaas P. Pruessmann
- Institute for Biomedical EngineeringUniversity and ETH ZürichZürichSwitzerland
| | - Shaihan J. Malik
- Division of Imaging Sciences and Biomedical Engineering, King's College LondonSt. Thomas' HospitalLondonUK
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40
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Özbay PS, Duerst Y, Wilm BJ, Pruessmann KP, Nanz D. Enhanced quantitative susceptibility mapping (QSM) using real-time field control. Magn Reson Med 2017; 79:770-778. [DOI: 10.1002/mrm.26735] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 03/31/2017] [Accepted: 04/02/2017] [Indexed: 12/15/2022]
Affiliation(s)
- Pinar Senay Özbay
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology; Zurich Switzerland
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Yolanda Duerst
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Bertram Jakob Wilm
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Klaas Paul Pruessmann
- ETH Zurich and University of Zurich, Institute for Biomedical Engineering; Zurich Switzerland
| | - Daniel Nanz
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology; Zurich Switzerland
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41
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Diffusion MRI of the human brain at ultra-high field (UHF): A review. Neuroimage 2017; 168:172-180. [PMID: 28428047 DOI: 10.1016/j.neuroimage.2017.04.037] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Revised: 04/14/2017] [Accepted: 04/15/2017] [Indexed: 11/20/2022] Open
Abstract
The continued drive towards MRI scanners operating at increasingly higher main magnetic fields is primarily motivated by the maxim that more teslas mean more signal and lead to better images. This promise of increased signal, which cannot easily be achieved in other ways, encourages efforts to overcome the inextricable technical challenges which accompany this endeavor. Unlike for many applications, however, diffusion imaging is not currently able to directly reap these potential signal gains - at the time of writing it seems fair to say that, for matched gradient and RF hardware, the majority of diffusion images acquired at 7T, while comparable in quality to those achievable at 3T, do not demonstrate a clear advantage over what can be obtained at lower field. This does not mean that diffusion imaging at UHF is not a worthwhile pursuit - but more a reflection of the fact that the associated challenges are manifold - and converting the potential of higher field strengths into 'better' diffusion imaging is by no means a straightforward task. This article attempts to summarize the specific reasons that make diffusion imaging at UHF more complicated than one might expect, and to highlight the range of developments that have already been made which have enabled diffusion images of excellent quality to be acquired at 7T.
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42
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Deistung A, Schweser F, Reichenbach JR. Overview of quantitative susceptibility mapping. NMR IN BIOMEDICINE 2017; 30:e3569. [PMID: 27434134 DOI: 10.1002/nbm.3569] [Citation(s) in RCA: 167] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 05/03/2016] [Accepted: 05/09/2016] [Indexed: 06/06/2023]
Abstract
Magnetic susceptibility describes the magnetizability of a material to an applied magnetic field and represents an important parameter in the field of MRI. With the recently introduced method of quantitative susceptibility mapping (QSM) and its conceptual extension to susceptibility tensor imaging (STI), the non-invasive assessment of this important physical quantity has become possible with MRI. Both methods solve the ill-posed inverse problem to determine the magnetic susceptibility from local magnetic fields. Whilst QSM allows the extraction of the spatial distribution of the bulk magnetic susceptibility from a single measurement, STI enables the quantification of magnetic susceptibility anisotropy, but requires multiple measurements with different orientations of the object relative to the main static magnetic field. In this review, we briefly recapitulate the fundamental theoretical foundation of QSM and STI, as well as computational strategies for the characterization of magnetic susceptibility with MRI phase data. In the second part, we provide an overview of current methodological and clinical applications of QSM with a focus on brain imaging. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Andreas Deistung
- Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany
| | - Ferdinand Schweser
- Buffalo Neuroimaging Analysis Center, Department of Neurology, Jacobs School of Medicine and Biomedical Sciences, The State University of New York at Buffalo, NY, USA
- MRI Clinical and Translational Research Center, Jacobs School of Medicine and Biomedical Sciences, The State University of New York at Buffalo, NY, USA
| | - Jürgen R Reichenbach
- Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany
- Michael Stifel Center for Data-driven and Simulation Science Jena, Friedrich Schiller University Jena, Jena, Germany
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43
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Gross S, Vionnet L, Kasper L, Dietrich BE, Pruessmann KP. Physiology recording with magnetic field probes for fMRI denoising. Neuroimage 2017; 154:106-114. [PMID: 28088483 DOI: 10.1016/j.neuroimage.2017.01.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 12/28/2016] [Accepted: 01/10/2017] [Indexed: 10/20/2022] Open
Abstract
Physiological noise originating in cardiovascular and respiratory processes is a substantial confound in BOLD fMRI. When unaccounted for it reduces the temporal SNR and causes error in inferred brain activity and connectivity. Physiology correction typically relies on auxiliary measurements with peripheral devices such as ECG, pulse oximeters, and breathing belts. These require direct skin contact or at least a tight fit, impairing subject comfort and adding to the setup time. In this work, we explore a touch-free alternative for physiology recording, using magnetic detection with NMR field probes. Placed close to the chest such probes offer high sensitivity to cardiovascular and respiratory dynamics without mechanical contact. This is demonstrated by physiology regression in a typical fMRI scenario at 7T, including validation against standard devices. The study confirms essentially equivalent performance of noise models based on conventional recordings and on field probes. It is shown that the field probes may be positioned in the subject's back such that they could be readily integrated in the patient table.
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Affiliation(s)
- Simon Gross
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Laetitia Vionnet
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Lars Kasper
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland; Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Wilfriedstrasse 6, 8032 Zurich, Switzerland.
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
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44
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Bollmann S, Kasper L, Vannesjo SJ, Diaconescu AO, Dietrich BE, Gross S, Stephan KE, Pruessmann KP. Analysis and correction of field fluctuations in fMRI data using field monitoring. Neuroimage 2017; 154:92-105. [PMID: 28077303 DOI: 10.1016/j.neuroimage.2017.01.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 01/06/2017] [Accepted: 01/06/2017] [Indexed: 10/20/2022] Open
Abstract
This work investigates the role of magnetic field fluctuations as a confound in fMRI. In standard fMRI experiments with single-shot EPI acquisition at 3 Tesla the uniform and gradient components of the magnetic field were recorded with NMR field sensors. By principal component analysis it is found that differences of field evolution between the EPI readouts are explainable by few components relating to slow and within-shot field dynamics of hardware and physiological origin. The impact of fluctuating field components is studied by selective data correction and assessment of its influence on image fluctuation and SFNR. Physiological field fluctuations, attributed to breathing, were found to be small relative to those of hardware origin. The dominant confounds were hardware-related and attributable to magnet drift and thermal changes. In raw image time series, field fluctuation caused significant SFNR loss, reflected by a 67% gain upon correction. Large part of this correction can be accomplished by traditional image realignment, which addresses slow and spatially uniform field changes. With realignment, explicit field correction increased the SFNR on the order of 6%. In conclusion, field fluctuations are a relevant confound in fMRI and can be addressed effectively by retrospective data correction. Based on the physics involved it is anticipated that the advantage of full field correction increases with field strength, with non-Cartesian readouts, and upon phase-sensitive BOLD analysis.
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Affiliation(s)
- Saskia Bollmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland.
| | - Lars Kasper
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland; Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich and ETH Zurich, 8032 Zurich, Switzerland
| | - S Johanna Vannesjo
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - Andreea O Diaconescu
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich and ETH Zurich, 8032 Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
| | - Klaas E Stephan
- Translational Neuromodeling Unit (TNU), Institute for Biomedical Engineering, University of Zurich and ETH Zurich, 8032 Zurich, Switzerland; Wellcome Trust Centre for Neuroimaging, University College London, London WC1N 3BG, UK; Max Planck Institute for Metabolism Research, 50931 Cologne, Germany
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, 8092 Zurich, Switzerland
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45
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Wezel J, Boer VO, van der Velden TA, Webb AG, Klomp DWJ, Versluis MJ, van Osch MJP, Garpebring A. A comparison of navigators, snap-shot field monitoring, and probe-based field model training for correcting B 0 -induced artifacts in T2*-weighted images at 7 T. Magn Reson Med 2016; 78:1373-1382. [PMID: 27859614 DOI: 10.1002/mrm.26524] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 09/27/2016] [Accepted: 10/02/2016] [Indexed: 11/06/2022]
Abstract
PURPOSE To compare methods for estimating B0 maps used in retrospective correction of high-resolution anatomical images at ultra-high field strength. The B0 maps were obtained using three methods: (1) 1D navigators and coil sensitivities, (2) field probe (FP) data and a low-order spherical harmonics model, and (3) FP data and a training-based model. METHODS Data from nine subjects were acquired while they performed activities inducing B0 field fluctuations. Estimated B0 fields were compared with reference data, and the reductions of artifacts were compared in corrected T2* images. RESULTS Reduction of sum-of-squares difference relative to a reference image was evaluated, and Method 1 yielded the largest artifact reduction: 27 ± 15%, 20 ± 18% (mean ± 1 standard deviation) for deep breathing and combined deep breathing and hand motion activities. Method 3 performed almost as well (24 ± 18%, 15 ± 17%), provided that adequate training data were used, and Method 2 gave a similar result (21 ± 16%, 19 ± 17%). CONCLUSION This study confirms that all of the investigated methods can be used in retrospective image correction. In terms of image quality, Method 1 had a small advantage, whereas the FP-based methods measured the B0 field slightly more accurately. The specific strengths and weaknesses of FPs and navigators should therefore be considered when determining which B0 -estimation method to use. Magn Reson Med 78:1373-1382, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Joep Wezel
- C.J. Gorter Center for high field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Vincent O Boer
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Tijl A van der Velden
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Andrew G Webb
- C.J. Gorter Center for high field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Dennis W J Klomp
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Matthias J P van Osch
- C.J. Gorter Center for high field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Anders Garpebring
- C.J. Gorter Center for high field MRI, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.,Department of Radiation Sciences, Umeå University, Umeå, Sweden
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46
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Brunner DO, Dietrich BE, Çavuşoğlu M, Wilm BJ, Schmid T, Gross S, Barmet C, Pruessmann KP. Concurrent recording of RF pulses and gradient fields - comprehensive field monitoring for MRI. NMR IN BIOMEDICINE 2016; 29:1162-1172. [PMID: 26269210 DOI: 10.1002/nbm.3359] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 05/26/2015] [Accepted: 06/18/2015] [Indexed: 06/04/2023]
Abstract
Reconstruction of MRI data is based on exact knowledge of all magnetic field dynamics, since the interplay of RF and gradient pulses generates the signal, defines the contrast and forms the basis of resolution in spatial and spectral dimensions. Deviations caused by various sources, such as system imperfections, delays, eddy currents, drifts or externally induced fields, can therefore critically limit the accuracy of MRI examinations. This is true especially at ultra-high fields, because many error terms scale with the main field strength, and higher available SNR renders even smaller errors relevant. Higher baseline field also often requires higher acquisition bandwidths and faster signal encoding, increasing hardware demands and the severity of many types of hardware imperfection. To address field imperfections comprehensively, in this work we propose to expand the concept of magnetic field monitoring to also encompass the recording of RF fields. In this way, all dynamic magnetic fields relevant for spin evolution are covered, including low- to audio-frequency magnetic fields as produced by main magnets, gradients and shim systems, as well as RF pulses generated with single- and multiple-channel transmission systems. The proposed approach permits field measurements concurrently with actual MRI procedures on a strict common time base. The combined measurement is achieved with an array of miniaturized field probes that measure low- to audio-frequency fields via (19) F NMR and simultaneously pick up RF pulses in the MRI system's (1) H transmit band. Field recordings can form the basis of system calibration, retrospective correction of imaging data or closed-loop feedback correction, all of which hold potential to render MRI more robust and relax hardware requirements. The proposed approach is demonstrated for a range of imaging methods performed on a 7 T human MRI system, including accelerated multiple-channel RF pulses. Copyright © 2015 John Wiley & Sons, Ltd.
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Affiliation(s)
- David O Brunner
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Benjamin E Dietrich
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Mustafa Çavuşoğlu
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
- Skope Magnetic Resonance Technologies, Zurich, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Christoph Barmet
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
- Skope Magnetic Resonance Technologies, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
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47
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Wezel J, Garpebring A, Webb AG, van Osch MJ, Beenakker JWM. Automated eye blink detection and correction method for clinical MR eye imaging. Magn Reson Med 2016; 78:165-171. [DOI: 10.1002/mrm.26355] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 06/14/2016] [Accepted: 07/05/2016] [Indexed: 12/13/2022]
Affiliation(s)
- Joep Wezel
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
| | - Anders Garpebring
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
- Radiation Sciences; Umeå University; Umeå Sweden
| | - Andrew G. Webb
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
| | - Matthias J.P. van Osch
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
| | - Jan-Willem M. Beenakker
- C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center; Leiden The Netherlands
- Department of Ophthalmology; Leiden University Medical Center; Leiden The Netherlands
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48
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Duerst Y, Wilm BJ, Wyss M, Dietrich BE, Gross S, Schmid T, Brunner DO, Pruessmann KP. Utility of real-time field control in T2
*-Weighted head MRI at 7T. Magn Reson Med 2015; 76:430-9. [DOI: 10.1002/mrm.25838] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 06/12/2015] [Accepted: 06/19/2015] [Indexed: 01/05/2023]
Affiliation(s)
- Yolanda Duerst
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
| | - Bertram J. Wilm
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
- Skope Magnetic Resonance Technologies; Zurich Switzerland
| | - Michael Wyss
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
| | - Benjamin E. Dietrich
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
| | - David O. Brunner
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Zurich Switzerland
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Vannesjo SJ, Graedel NN, Kasper L, Gross S, Busch J, Haeberlin M, Barmet C, Pruessmann KP. Image reconstruction using a gradient impulse response model for trajectory prediction. Magn Reson Med 2015. [PMID: 26211410 DOI: 10.1002/mrm.25841] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE Gradient imperfections remain a challenge in MRI, especially for sequences relying on long imaging readouts. This work aims to explore image reconstruction based on k-space trajectories predicted by an impulse response model of the gradient system. THEORY AND METHODS Gradient characterization was performed twice with 3 years interval on a commercial 3 Tesla (T) system. The measured gradient impulse response functions were used to predict actual k-space trajectories for single-shot echo-planar imaging (EPI), spiral and variable-speed EPI sequences. Image reconstruction based on the predicted trajectories was performed for phantom and in vivo data. Resulting images were compared with reconstructions based on concurrent field monitoring, separate trajectory measurements, and nominal trajectories. RESULTS Image reconstruction using model-based trajectories yielded high-quality images, comparable to using separate trajectory measurements. Compared with using nominal trajectories, it strongly reduced ghosting, blurring, and geometric distortion. Equivalent image quality was obtained with the recent characterization and that performed 3 years prior. CONCLUSION Model-based trajectory prediction enables high-quality image reconstruction for technically challenging sequences such as single-shot EPI and spiral imaging. It thus holds great promise for fast structural imaging and advanced neuroimaging techniques, including functional MRI, diffusion tensor imaging, and arterial spin labeling. The method can be based on a one-time system characterization as demonstrated by successful use of 3-year-old calibration data. Magn Reson Med 76:45-58, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- S Johanna Vannesjo
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Nadine N Graedel
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Lars Kasper
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.,Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Julia Busch
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Maximilian Haeberlin
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Christoph Barmet
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland.,Skope Magnetic Resonance Technologies, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
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50
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Wilm BJ, Nagy Z, Barmet C, Vannesjo SJ, Kasper L, Haeberlin M, Gross S, Dietrich BE, Brunner DO, Schmid T, Pruessmann KP. Diffusion MRI with concurrent magnetic field monitoring. Magn Reson Med 2015; 74:925-33. [DOI: 10.1002/mrm.25827] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 06/08/2015] [Accepted: 06/09/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Bertram J. Wilm
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
| | - Zoltan Nagy
- Laboratory for Social and Neural Systems Research; University of Zurich; Switzerland
| | - Christoph Barmet
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
- Skope Magnetic Resonance Technologies LCC; Zurich Switzerland
| | - S. Johanna Vannesjo
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
| | - Lars Kasper
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
- Translational Neuromodeling Unit; Institute for Biomedical Engineering, University of Zurich and ETH Zurich; Switzerland
| | - Max Haeberlin
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
| | - Benjamin E. Dietrich
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
| | - David O. Brunner
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering; University of Zurich and ETH Zurich; Switzerland
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